1. Field of the Invention
This invention relates to a 10-carat gold alloy comprising 41.7% gold and alloying constituents consisting of silver, copper, and zinc.
2. Description of the Prior Art
As the gold content of a gold alloy decreases, it will be increasingly more difficult to provide an alloy having the typically gold-yellow hue which is desired by the buyers of ornaments. Besides, the composition of the alloy must be determined not only with a view to its hue but also with a view to the processing properties of the alloy. For this reason, two types of alloys have been successful among low-carat gold alloys (8 carats, 9 carats, 10 carats), namely, in the first place, which can be processed in chain-making machines and for this reason is relatively soft because it has relatively high brass and copper contents so that the alloy has a reddish hue, which is not particularly desired by the buyers. The other alloy is used for making (centrifugally) cast ornaments and for this reason must be much harder and for that purpose has a higher silver content so that the alloy is light-yellow and paler than is desired.
For this reason it is usual in the making of ornaments from low-carat gold alloys to correct the hue in that the ornaments is plated with a very thin gold layer by a treatment in a high-carat electrolytic gold bath. Such a thin gold layer is also described as a flash.
French Patent Specification 2,305,523 discloses a 5-carat gold alloy which contains 37,5% gold, 38,5 to 59% copper, 3.5 to 9% silver, and 0 to 15% zinc. That alloy has allegedly good soldering properties but owing to its wide composition ranges its hue and its processing properties may be within such wide ranges that they cannot be defined by statements which would be applicable in general.
German Patent Specification 30 01 591 discloses a 10-carat gold alloy which contains 43.8 to 44.9% copper, 7.9 to 9.44% silver, and 3.9 to 6.5% zinc. A 10-carat gold alloy containing 44 to 44.7% copper, 8.3 to 9% silver, and 4.5 to 5.9% zinc is preferred. That alloy is allegedly deformable and requires no very thin gold plating. But it is too reddish to be favored by the public and is too soft for a convenient processing (except on chain-making machines). Whereas the hue might be improved by an addition of nickel, nickel is increasingly rejected because it is not compatible (nickel allergy) and for this reason can no longer be added to alloys for ornaments.